[Engine-devel] Empty cdrom drive.

[Igor Lvovsky]

  Hi,
I want to discuss $subject on the email just to be sure that we all on the
same page.

So, today in 3.0 vdsm has two ways to create VM with cdrom :
 1. If RHEV-M ask to create VM with cdrom, vdsm just create it
 2. RHEV-M doesn't ask to create VM with cdrom, vdsm still creates VM with
    empty cdrom. Vdsm creates this device as 'hdc' (IDE device, index 2),
    because of libvirt restrictions.
    In this case RHEV-M will be able to "insert" cdrom on the fly with
    changeCD request.

In the new style API we want to get rid from stupid scenario #2, because 
we want to be able to create VM without cdrom at all.
It means, that now we need to change a little our scenarios:
 1. If RHEV-M ask to create VM with cdrom, vdsm just create it
 2. RHEV-M doesn't want to create VM with cdrom, but it want to be able to
    "insert" cdrom on the fly after this. Here we have two options:
    a. RHEV-M should to pass empty cdrom device on VM creation and use
       regular changeCD after that
    b. RHEV-M can create VM without cdrom and add cdrom later through
       hotplugDisk command.

Note: The new libvirt remove previous restriction on cdrom devices. Now
      cdrom can be created as IDE or VIRTIO device in any index. 
      It means we can easily hotplug it.


Regards,
    Igor Lvovsky